Casting method



Aug. 6, 1968 E. A. THOMPSON CAST I NG METHOD 6 Sheets-Sheet 1 INVENTOR.

EARL A. THOMPSON i zw AGENT 1968 E. A. THOMPSON 3,395,747

CASTING METHOD Filed Sept. 4, 1962 6 Sheets-Sheet 3 dm/llllg g INVENTOR.

EARL A. THOMPSON AGENT E. A. THOMPSON 3,395,747

CASTING METHOD 1962 6 Sheets-Sheet 5 Aug. 6, 1968 Filed Sept. 4

INVENTOR. gKARL A. THOMPSON fi,

Qm Nb AGENT 6, 1958 E. A THOMPSON 3,395,747

CAST ING METHOD Filed Sept. 4, 1962 6 Sheets-Sheet 6 INVENTOR.

gARL A. THOMPSON AGENT United States Patent m 3,395,747 CASTING METHODEarl A. Thompson, 1300 Hilton Road, Ferndale, Mich. 48220 Filed Sept. 4,1962, Ser. No. 221,115 21 Claims. (Cl. 164-95) This invention relates tocomposite casting, and more particularly to method and apparatus forcontinuously casting improved multi-metal articles, such as exhaustvalves for the combustion chambers of internal combustion engines.

While the method and apparatus of this invention are capable ofproducing various products having particular, but differingmetallurgical characteristics in separate portions of the article,exhaust valves for combustion engines aptly illustrate one such product.

Valves currently in use are subject to extremely ad- Verse operatingconditions. The head must function in temperatures above 1500 F. incertain modern automotive engines utilizing high octane fuels, and itmust resist corrosion from the combustion products of such leaded fuels.It must also have high impact strength under these unfavorableconditions to withstand abrupt, high seating loads. The bevelled orconical seating perimeter of the valve head, on the other hand, must beeven further resistant to corrosion and metal to metal wear, but neednot have the low cost, high strength and toughness characteristics ofthe flared head itself. The valve stem, moreover, while operating atsomewhat lower temperatures than the seating area, must have additionalresistance to abrasion and wear in the valve guide and particularly fromthe actuating cam or rocker arm.

The valve art is crowded with various proposals to meet these needs,none of which have provided ultimate solutions in the practical sense.Attainment of all the desired exhaust valve properties in a single alloyappears to be at best a prohibitively expensive compromise.

Forming the parts of the valve of separate alloys parts welded togetheralso is expensive, and the weld joints often fall short of the desiredstandard. For instance, in the past an upset or extruded austeniticsteel head, which has the desired performance and cost qualities, hashad welded or puddled therearound a facing of expensive cobalt-basemetal to form the seat. But the different coefiicients of thermalexpansion of these two metals obviously creates an unbalance ofexpansion forces at different temperatures acting on the joint betweenthe two; and, the weld represents an interruption extendig across theradial paths along which heat is conducted away from the hot center ofthe head to the seating area. Additionally, welding a carbon steel tipof the hardenable martensitic type to the end of the austenitic steelvalve stem represents a further expensive processing step.

Accordingly, it is an object of the present invention to form improvedexhaust valves inexpensively by casting suitable separate metalssequentially into the ap propriate places in a mold to form anautogenously united cast valve exhibiting the desired qualities in eachportion thereof without the disadvantages of welded joints.

Another object of this invention is to provide 'an improved castingmethod for continuously producing multimetal articles which utilizesforces other than gravity to locate molten metal in the desired portionof the mold to form one portion of the article and also utilizes gravityto locate other molten metal in the mold to form another portion of thesame article.

Another object of this invention is to provide an improved continuouscast-ing apparatus including means for imparting centrifugal force tometal in a mold.

Another object of this invention is to provide, in combination with acontinuous centrifugal casting machine 3,395,747 Patented Aug. 6, 1968for composite casting, a 'mechanico-hydraulic motivator of the rotarycam and liquid column type.

Another object of this invention is to provide a cast engine valve ofimproved metallurgical quality.

Further objects and advantages of the present invention will be apparentfrom the following detailed description, with reference to theaccompanying drawings in which like reference characters refer to thesame parts throughout the several views, and in which:

FIGURE 1 is a general plan view showing the major components of thecasting machine of this invention;

FIGURE 2 is a fragmentary sectional elevational view showing the indextable and a pouring station of the machine;

FIGURE 3 is a sectional view on line 33 of FIGURE 2 showing details ofthe indexing mechanism;

FIGURE 4 is an enlarged plan view with parts broken away showing thegeneral scheme of the transfer arm loading means for fresh molds;

FIGURE 5 is a sectional view showing the mechanism for swinging andelevating a transfer arm;

FIGURE 6 is a sectional view on line 66 of FIG- URE 5 showing the fluidmotor for swinging a transfer arm;

FIGURE 7 is a plan view showing the general scheme of the transfer armunloading means for filled molds;

FIGURE 8 is an enlarged sectional view of the compensating arrangementfor the metal metering valve of a pouring station;

FIGURE 9 is an enlarged sectional view of a spindled mold holder on theindex table periphery;

FIGURE 10a is a schematic view of the controls for themechanico-hydraulic motivator for the machine of this invention;

FIGURE 10b is a schematic view of the actuating portion of themechanico-hydraulic motivator connected with the fluid motors on thecasting machine;

FIGURES ll, 12 and 13 are fragmentary sectional views through a moldillustrating different steps in the casting process;

FIGURE 14 is an elevational view partly in section of a product castaccording to this invention; and

FIGURE 15 is a view of a product such as an internal combustion enginevalve in its functional environment.

Referring to FIGURES 1 through 10b, the preferred embodiment of acomposite centrifugal casting machine is disclosed. Generally, an indexmember such as an intermittently shiftable rotary table 10 moves moldholders 12 spaced around its periphery past a series of stationsincluding a fresh mold loading station 14, a mold holder rotatingstation 16, a first metal pouring station 18, a second such station 20-,a mold holder slow down station 22, a third metal pouring station 24,and a filled mold unloading station 26.

The shiftable table member 10 is supported on a base or pedestal 30located on a foundry floor 32, see FIG- URE 2. Beneath the table 10, aninner thrust bearing race 34 may be secured by fasteners 36, and theinner portion of the race may further include a ring of internal gearteeth 38. An outer bearing race 40 may be secured in a horizontal planeto the base 30 by fasteners 42 in a position to retain ball bearings 44and thus support the table 10 for rotary motion.

Drive mechanism for the table may include a pinion 46 meshing with thegear teeth 38 of the table and driven by a vertical shaft 48 which isjournalled in and axially shiftable through suitable bearings 50 in themachine base. Pinion teeth 52 integral with the shaft are engaged by theteeth of a sliding rack 54. A pair of U-cup sealed piston faces 56 (FIG.3) on either end of the rack 54 reciprocate in aligned cylinders 58 toshift the rack to and fro between adjustable limit stops 60. Pressurizedfluid admitted through a connection 62 at one end of the cylinderarrangement rotates the drive pinion 48 in the resetting direction, andpulsator fluid admitted to the other end through a connection 64 rotatesthe drive pinion to index the table member 10.

The lower end of the pinion shaft 48 has a swivel connection 66 with theupper end of the rod 68 of a piston 70 vertically slidable in a cylinder72 in the machine base. Pressurized fluid admitted to the cylinder 72through a connection 74 biases the shaft downwardly to disengage thedrive pinion 46 from the table gear teeth 38, and hydraulic fluidadmitted through a connection 76- elevates the drive pinion to engagethe teeth 38. It will be noted that the pinion teeth 52 are axiallyelongated so as to retain their meshing engagement with the rack 54 asthe shaft 48 is raised and lowered.

When the table 10 has been indexed through a small predetermined numberof degrees of angular motion and the drive pinion 46 is lowered so thatthe rack 54 may be reset, a locking and locating device may becomeoperative. Such a device may include a gear tooth 78 secured to the rod80 of a piston 82 axially shiftable in a cylinder 84. Hydraulic fluidadmitted to the cylinder 84 through a connection 86 retracts the piston82 and allows rotary motion of the table 10. Hydraulic fluid admitted tothe other end of the cylinder 84 through a connection '88 shifts thepiston 82 to engage the gear tooth 78 with a tooth of the ring of gearteeth 38 on the table. This accurately locates and locks the table inposition while metal is being poured into one of the molds, and whilethe drive gear 46 is lowered for resetting.

For loading and unloading the molds to and from the holders 12 on theshiftable member 10, a. pair of transfer arms may be provided (FIG. 1),one at the first station 14 ahead of the plurality of pouring stationsand one at the final station 26 following the series of pouringstations. The loading means 90 at the first station is illustrated inFIGURE 4; the unloading means 92 at the final station is illustrated inFIGURE 7. Both means may comprise horizontally swinging transfer armswith a gripper at the outer end and an elevating mechanism at the pivot,and they may be identical in structure differing only in operationaltiming of moving parts-- thus detailed description of one will sufficeto disclose the structure of both.

As can be seen in FIGURES 4-6, such a transfer arm may comprise agenerally horizontally extending swinging body member 94 fixed at oneend on a vertical pivot shaft 96 which is journalled in and axiallyshiftable through suitable bearings 98 in the machine base (FIG. Pinionteeth 100 integral with the pivot shaft are engaged by the teeth of aslida'ble rack 102. A pair of U-cup sealed piston faces 104 (FIG. 6) oneither end of the rack 102 reciprocate in aligned cylinders 106 to shiftthe rack to and fro between adjustable limit stops 108. Pressurizedfluid admitted through a connection 110 swings the arm away from theindex member 10, and pulsator fluid admitted through a connection 112swings the arm in the opposite direction toward the table as can beunderstood.

The lower end of the arm pivot shaft 9 6 has a swivel connection 114(FIG. 5) with the upper end of the rod 116 of a piston 118 verticallyreciprocable in a cylinder 120 in the machine base. Pressurized fluidadmitted to the cylinder 120 through a connection 122 biases the shaftdownwardly on the machine base, and hydraulic medium admitted through aconnection 124 elevates the shaft 96 and consequently lifts the arm 94bodily upward at predetermined distance. It will be noted that thepinion teeth 100 are axially elongated so as to retain their meshingengagement with the rack 102 as the arm is raised and lowered.

On the outer end of such a transfer arm, a pair f gripper jaws 126 areshiftable in opposition to one another along the arm axis. They shift inunison by means of a common double rack and central pinion assembly 128(FIG. 4) housed in the arm itself. Double piston-cylinder arrangement130 in the arm serves to close the jaws when subjected to hydraulicpressure through a connection 132, and open the jaws when subjected tohydraulic pressure through a connection 134.

The transfer arms may be operated by the mechanicohydraulic motivator(explained in detail below) in the following fashion. First, the jaws ofthe loading arm 90 close to grip a fresh shell mold at the supplystation 14 continuously replenished with fresh molds by suitable meanssuch as an endless belt 136. Then the loading arm israised to lift themold clear of guide rails 138 at the supply station so that it may swingclockwise (FIG- URE 4) to position the gripped mold over a holder 12presented at the loading station. Lowering of the arm and subsequentopening of the jaws serves to deposit the mold on the index member,which may begin its next indexing movement prior to the arm swingingcounter-clockwise back to the mold supply station.

The unloading arm 92 (FIGURE 7) may move through a somewhat differentcycle. As a filled mold is indexed by the member 10 to the unloadingstation 26, the jaws of the unloading arm close to grip the mold,crunching through any loose sand if necessary and engaging the coolingcasting. Then the arm will raise bodily, lifting the casting clear ofthe fixture 12 free to swing counter-clockwise to a position above ashaker screen 140. At this point, the jaws may open and allow theworkpiece to drop to the screen which will vibrate it away toward asubsequent operation, freeing the casting of loose sand as it goes. Theunloading arm may then be lowered as it is returned in a clockwisedirection to receive the next filled shell mold. Thus, the loading andunloading means, while identical in structure, follow different programsto render the composite casting apparatus of this invention entirelyautomatic and well suited to modern high volume mass productionrequirements.

Between the loading station 14 and the first metal pouring station 18, amold rotating station 16 may include below the table edge a drive meanssuch as an electric motor 142 connected to spin a fiber drive wheel 144.The motor 142 may be mounted on a support 146 pivoted to the machinebase at 148 to swing the drive wheel 144 toward and from the circularpath of the mold holders 12. A fluid motor 150 may be connectedtherewith to control such shifting in timed relation with movement ofthe table 10.

The trio of metal pouring stations 18, 20 and 24 may each include abottom pour induction heated container, illustrated in the upper portionof FIGURE 2. T he pouring stations may be comprised of similar elements,thus description of station 18 will provide a disclosure of all;structural elements of the pouring station 20 will be designated bysimilar reference numerals with the addition of a prime mark, andstructural elements of the pouring station 24 will be designated bysimilar reference numerals with the addition of a double prime mark.

Station 18 may include a casting furnace 152 comprising an inductionheating coil 154 concentrically surrounding a container 156 of generallyupright cylindrical configuration and may be separated therefrom by acentering and insulating layer of packed casting sand 158. The container156 and heating arrangement 154 may be sup ported upon suitable slabs ofrefractory or ceramic material located upon a framework 160, and may beseparately replaceable as a unit on the framework to ex-- I change onesuch furnace for another of different characteristics required forcasting, for instance, of a different article. A split disc-shaped cover162 conserves the continuously generated anti-oxide atmosphere.

In" addition to removably locating each casting furnace relative to thetable 10, the framework 160 further supports actuating mechanism forvalving arrangements constructed to meter predetermined small amounts ofmolten metal from the casting furnaces to a mold positioned on thetable. Such a valving mechanism may comprise an elongated shiftablevalve member 164 of refractory material having a semi-spherical bottomend portion 166 extending down into the container 156, and an upperportion 168 extending above the container 156. An actuating lever 170fulcrumed at 172 on the framework 160 may be pivotally connected at 174with the upper portion 168 of the valve member. Oscillation of the lever170 in a vertical plane about its horizontal fulcrum pivot axis 172 willimpart small up-and-down movement to the valve member. Such motion maybe effected by a fluid motor 176 fixed on the framework having an upperconnection 178 through which hydraulic medium may be pulsed to lift thevalve member 164, and a lower connection 180 through which hydraulicmedium may be introduced to bias the valve member 164 downwardly in thecontainer 156.

Connecting the lever 170 with the piston rod 182 of the fluid motor 176is a compensating mechanism 184 to automatically adjust the valveactuating linkage to accommodate thermal expansion or contraction of theelongated valve r-od member 164. One form of such a compensator maycomprise a housing 186 including external pivot connections 188 with thelever means 170, and a central piston rod receiving aperture 190extending therethrough in a direction normal to the axis of the pivotconnection 188. A flexible sleeve 192 may be located within the aperture190, and may be formed by longitudinal slots 194 in a metal sleevehaving a relaxed, normal internal diameter only slightly larger than thediameter of the piston rod 182 of the fluid motor 176. A plunger 196 ina laterally extending section of the housing 186 of the compensator mayradially abut the split end of the sleeve 192. Hydraulic fluid pulsedthrough a connection 198 in an end of the housing section serves to biasthe plunger 196 laterally against the resilient sleeve 192 and thusclamp the piston rod 182 in a fixed relation to the lever pivot 188.When the valve actuating mechanism is not being operated, and the fluidmotor 176 is in its rest position, fluid pressure may be relieved frombehind the plunger 196 whereby the inherent resiliency of the splitsleeve 192 will restore its normal internal diameter, thus allowing atelescopically sliding compensating adjustment of the connection betweenthe lever pivot 188 and the piston rod 182.

A valve seating spring 200, the tension of which may be adjusted by anut 202 on the threaded terminus of the piston rod 182, may be employedto bias the housing 186 upwardly to thus impart a desired downwardseating pressure :on the valve member 164 in the container 156 when thevalve is not being actuated by the fluid motor 176.

The lower rounded end 166 of the valve rod member 164 may extenddownwardly into the molten metal in the container 156 and matinglyengage an upwardly facing dished valve seat 204 formed in an annularsupport 206 also of refractory material. The support 206 may include anouter shoulder 208 separating larger and smaller outer diameter portionsthereof. The smaller outer diameter portion may be snugly received in anaperture 210 in the bottom wall of the container 156 and its supportingstructure, and the larger outer diameter portion may extend upwardlytherefrom to position the valve seat 204 away from the container wallwhereby molten metal will essentially surround the valving mechanism.

Internally, the support 206 may include a generally downwardly directeddelivery port 212 having a narrow upper portion 214 communicating withthe valve seat 204, and a wider lower portion 216 opening below thesupporting structure 160 for the casting furnace 152. The upper andlower portions of the delivery opening may be connected by a reverseangle shoulder forming a depending or overhanging internal lip 218. Sucha lip may be located in the upper portion of the support 206, within therange of the heating coil 154 and the high temperature molten metalwhich essentially surrounds the valving mechanism. This insures that nometal will freeze in the delivery opening and disrupt operation of thevalving mechanism. The entire support 206 including the delivery openingand valve seat may be formed as a replaceable insert whereby a new unitmay be substituted for a worn one with very little effort. Furthermore,since the size of the delivery opening 214 governs the rate of flow fromthe container 156-viscosity and static head remaining constant-theamount of metal metered in a given time may be varied simply byreplacing valve seat inserts 206 to utilize the desired orifice size forthe particular product being cast.

Between the pouring stations 20 and 24, the station 22 may include abrake to stop rotation of each individual mold holder. Such a device mayinclude a brake shoe 220 secured to the end of the shiftable piston rod222 of a fluid motor 224. When the shoe 220 is shifted by the motor 224slowly toward the circular path of the mold holders 12, rotary motion ofeach holder will be stopped.

The mold holders 12, a plurality of which are positioned around thetable 10, are identical in structure, and again a description of onewill provide a disclosure of all. Regarding FIGURE 9, each holder 12 maybe constructed as a quickly replaceable cartridge unit having an outerflanged insert section 226 insertable in a shouldered aperture 228 inthe table 10. The section 226 provides a support for the outer races ofa pair of bearings 239, the inner races of which support a hollowspindle 232. A nut 234 threaded on the lower end of the spindle 232secures the hearings in thrusting relation against an upper shoulder236. The bearings are shielded from above by a brass cover 238, and thehollow center 240 of the spindle is adapted to allow metal metered froma pouring station to fall on through without injuring the table 10 andholder 12 if by accident there is no mold positioned on the holder. Theupper portion of the spindle center 240 is tapered outwardly at 242 todrivingly receive a mold.

Below the table 10, each spindle 232 may include a centrally aperturedflywheel 244 removably secured theron by a second nut 246 threaded onthe lower end of the spindle. Rotary motion may be imparted to thespindled mold holder by engaging the spinning fiber Wheel 144 directlywith the flywheel 244, as can be understood, and such rotary motion willbe maintained by the appropriately massive flywheel.

For the purpose of giving coordinated motivation to the various fluidmotors described above, there is provided a mechanico-hydraulicprogramming system for producing a cycle of coordinated movement,illustrated diagrammatically in FIGURES 10a and 10b. This system may beconstructed as a self-contained unit having its own housing, notillustrated, which may be positioned at any convenient location on oradjacent the casting machine and connected to the various hydrauliccylinders by a suitable flexible piping. The mechanico-hydraulic driveunit comprises a master camshaft 250 carrying a plurality of cams 252,the followers of which operate the transmitter pistons 254, each ofwhich forms a part of a liquid column type motion transfer device ofwhich there are seventeen units shown in the diagram of FIGURE 10b. Eachpiston reciprocates in a cylinder 256 having a head B which contains asuitable inlet replenishing check valve 258 and a high pressure reliefvalve 260 both of which communicate with a low pressure oil reservoir2.62 preferably formed in a housing enclosing the drive unit.

For turning the camshaft 250, a motor 264 drives an input shaft 266 of atwo-speed transmission through a belt drive 268. The input shaft 266drives a pinion 270 and also the input member of ahydraulically-engaged, spring-released clutch 272. Pinion 270 drives agear 274 secured to a countershaft 276 which carries a pinion 278 at itsopposite end. Pinion 278 drives a gear 280 and therewith constitutes aset of change speed gears. Gear 280 drives the input member of a secondhydraulicallyengaged, spring-released clutch 282. The driven members ofclutches 272 and 282 are secured to the opposite ends of a shaft 284,having a worm 286 thereon and brake drum 288. The latter has aspring-biased hydraulic motor 290 for engaging the brake. Worm 286drives a worm wheel 292 secured to the master camshaft 250.

For the purpose of automatically controlling the starting, stopping, andspeed of the transmission, there is provided a hydraulic control pump294 driven from gear 280, which may circulate a body of oil contained inthe housing surrounding the transmission. The pump 294 may deliver to acombined accumulator and relief valve comprising a spring loaded piston296 and also supplies oil to a bank of control valves 298, 300 and 302.In the diagrams, each valve is shown as a two-position valve,spring-biased to the position illustrated in which the connections shownin the cross-hatched rectangles are established. Single-headed arrowsare used to indicate flow at reservoir pressure and double-headed arrowsto indicate flow at a pump delivery pressure. Each of the valves, whenshifted, establishes the connections shown in the unhatched rectanglesimmediately below the hatched rectangles.

Valve 298 is arranged to be shifted by a solenoid 304. Valves 300 and302 are arranged to be shifted by the adjustable cams 306 and 308,respectively, which are positioned on camshaft 250. In addition, thevalve 300 has a hydraulic holding cylinder 310 which holds the valve 300in its shifted position until it is released by the shifting of valve302. Valve 298 in the position shown delivers pressure fluid to engagethe brake 290 and also exhausts fluid to release the low speed cl-utch282. When shifted, valve 298 exhausts fluid to release brake 290 andsupplies pressure fluid to engage the low speed clutch 282, subject,however, to a conjoint control by the valve 300.

The latter valve, in the position illustrated, exhausts fluid to releasethe high speed clutch 272 and places the low speed clutch 282 under thecontrol of valve 298. In its shifted position, valve 300, provided valve298 has been shifted, delivers pressure fluid to engage high speedclutch 272 and exhausts fluid to release low speed clutch 282. Aspreviously explained, the valve 302 is merely a reset valve forby-passing the holding cylinder 310 to permit valve 300 to return to itsspring biased position shown in the drawings.

Thus, energization of solenoid 304 will start the camshaft rotating atslow speed. Thereafter, the cam 306 will shift the transmission to drivethe camshaft at high speed, and still later the cam 308 will againstshift the transmission to slow speed. So long as the solenoid 304remains energized, the camshaft 250 will continue to rotate, first at aslow speed and then at a high speed during each revolution, controllingits own speed changes by operation of the cams 306 and 308.

For the purpose of controlling the drive motor 263 and solenoid 304,there is provided an electric control circuit connected between a pairof electric supply lines, designated L1 and L2. The circuit may includea master relay 312 of the holding type having a manual master startswitch 314 and a manual master stop switch 316. Relay 312 controls themotor 264 and also a cycle control relay 318 of the holding type havinga manual cycle start switch 320 and a manual cycle stop switch 322. Thenormally open contacts of relay 318, which are of the makebefore-breaktype, control energization of cycle solenoid 304 directly. The normallyclosed contacts of relay 318 also control solenoid 304, but are inseries with a cam switch 324 on the end of, the camshaft 250 andarranged to be opened once during each revolution thereof. Thearrangement is such that when the cycle stop switch 322 is operated atany point in the rotation of camshaft 250, relay 318 will bede-energized, but solenoid 304 will remain energized until cam switch324 opens at the predetermined stopping point. Operation of the masterstop switch 316, however, will de-energize solenoid 304 immediately,regardless of the point also de-energize motor 264.

The camshaft 250 as previously mentioned drives a number of cam operatedhydraulic pulsator sections designated a through g, inclusive. Eachsection may comprise units duplicating the single acting pulsatingcylinder 256, the head B of which contains the replenishing check valve258 and the spring closed relief valve 260. All the re plenishing andrelief valves are connected to a common oil reservoir 262 formed in thehousing of the unit. The reservoir 262 is preferably subjected to a low,super-atmospheric pressure by a body of compressed air or other pressuremaintaining arrangements. Check valves 258 allow flow from the reservoir262 to the cylinder 256, while relief valves 260 allow flow oppositelywhen the cylinder pressure exceeds a certain value. Thus each of thepairs of valves 258 and 260 may be referred to as a balancing valve andserve to balance the volume of fluid in each of the liquid columnsection.

In order to insure proper synchronization of the driving and drivenelements of each pulsator section, it is desirable to provide slightlymore fluid displacement in the driving or transmitting elements 252256than is present in their respective fluid motors at the opposite end ofthe liquid column line. Thus at the end of each advancing stroke of thetransmitter piston 254, a small amount of fluid will be discharged toreservoir 262 through its relief valve 260. This amount plus any amountlost by leakage will be returned to the liquid column at the end of thereturn stroke by the operation of the replenishing valve 258.

In FIGURE 10!; there are shown several circles marked R0 connected tothe end of some of the motive cylinders opposite the liquid columnconnections. These symbols designate the return oil connections by meansof which a pulsator system may be hydraulically biased so as to maintainthe follower in close contact with the cam as the falling portion of thecam contour recedes from the follower. This bias is maintained by a highpressure accumulator or oil reservoir, not shown, which may be providedwith a manifold whereby all of the RO connections are joined togetherand to the high pressure reservoir. The showing of separate return oilconnections in FIGURE 10b is indicative of any suitable type of biasingpressure source, whether it be a single accumulator or multiplicitythereof. The contours of the individual cams 252 are likewise notillustrated in specific detail since they may be formed in accordancewith the usual practice to cause motivation of each of the respectivehydraulic motors in accordance with the particular operating cycledesired for the machine. Likewise the speed ratio between the high andlow speeds of the camshaft 250, and the duration of the high speedportion of the cycle, may be selected as desired through use of theappropriate change gears 270280 and through the adjustment of the cams306 and 308, if desired. Of course, the two speed feature of thetransmission may be omitted and the high speed clutch 272, the cams 306and 308 and the valves 300 and 302 eliminated.

As can be seen from FIGURE 10b, pulsator section a is connected by itsclosed liquid column line 326a with the connection 88 of the tablelocating motor cylinder 84. Pulsator section b is connected by itsliquid column 32Gb with the jaw operating fluid motor means for theunloading arm 92. Pulsator section 0 is connected by its liquid column3260 with the connection 112 of the motor cylinder 106 for swinging theloading arm 90. Pulsator section d is connected by its liquid column326d with the arm elevating fluid motor for the unloading arm 92.Pulsator section e is connected by its liquid column 326a with theconnection 124 of the motor cylinder for elevating the loading arm 90.Pulsator section 1 is connected by its liquid column 326 with the armswinging fluid motor for the unloading arm 92. Pulsator section g isconnected by its liquid column 326g with the in the cycle and willconnection 134 of the jaw operating fluid motor means 130 for theloading arm 90. Pulsator section h is connected by its liquid column326k with the fluid motor 150 for swinging the spin imparting motoragainst each mold holder flywheel. Pulsator section i is connected byits liquid column 326i with the connection 178 of the metal meteringmotor 176. Pulsator section j is connected by its liquid column 326 withthe fluid motor 224 for shifting the brake 220 against each mold holderflywheel. Pulsator section k is connected by its liquid column 326k withthe connection 188 of the first metering valve com pensator. Pulsatorsection I is connected by its liquid column 3261 with the connection 76for raising the drive pinion 46 into engagement with the table gearteeth. Pulsator section In is connected by its liquid column 326m withthe connection 178 of the metal metering motor 176'. Pulsator section nis connected by its liquid column 326; with the connection 64 of thefluid motor cylinder 58 for oscillating the drive pinion 46 to drive thetable. Pulsator section is connected by its liquid column 3260 with theconnection 188' of the second metering valve compensator. Pulsatorsection p is connected by its liquid column 326p with the connection188" of the third metering valve compensator. And, pulsator section q isconnected by its liquid column 326: with the connection 178" of themetal metering motor 176".

It will be noted from FIGURE b that liquid column lines 3261', 326m and326: are interrupted by three-wlay, two position solenoid actuatedvalves 328, 330 and 332, respectively, spring biased to their normalpositions in which the connections shown in the cross hatched rectanglesare established. These are liquid column disabling valves which, in thenormal position shown, allow free operation of the liquid columns but,in the shifted position established the connections shown in theunhatched rectangles whereby the liquid columns are directly connected,or dumped, into the low pressure reservoir 262 thus allowing the fluidmotors 176, 176 and 176" to return to their normal posit-ions responsiveto the return bias from the source RO. This closes the metal meteringvalves at the pouring stations even though the cams at pulsator sections1', m land q still present rise contours to their respective followers.

The valves 328, 330 and 332 are each moved to their shifted position bytiming mechanisms 334, 336 and 338, respectively, individuallyadjustable to determine the length of time the metal metering valves areopened, and thus governing the amount of metal metered to the molds ateach of the pouring stations. Each timer is started during every cycleof the machine by suitable electric c'ircuitry of conventional designresponsive to a rotary cam activated limit switch 340. As each timertimes out and actuates the solenoid after the metal metering valve hasbeen opened by the cam at pulsator sections 1', m or q, the liquidcolumn is disabled and the valve is closed at the adjustable,predetermined time dictated by the timer. Later in the cycle, after thepulsator cams at these stations have again presented their base circlesto their fol lowers, a second cam operated limit switch 342 may beemployed to reset the two timers and deactivate the solenoids. Ifdesired, of course, the fine adjustment pro vided by the timers may beeliminated, and the metal metering valves may be controlled directly bythe cams at the respective pulsator sections.

The mold for articles cast on the above described machine may be of theshell mold variety. A shell mold 344 for an internal combustion enginevalve, for instance, may comprise an upper portion 346 and a lowerportion 348 bonded together to form an internal cavity 350 defining theshape of the valve to be cast. On the bottom of the lower section of themold, a tapered boss 352 may form a driving fit with the mating taper242 of the spindled mold holder 12. The upper part of the mold rn'ayflare out to form a feed pocket 354 for excess metal to feed the shrinkas the casting cools. It will be clear that any suitable mold may beemployed according to the article being cast, and the spindled holders12 adapted thereto.

In operation, with molten metal of the desired varieties in each of thecontainers 152, 152' and 152" at the pouring stations 18, 20 and 24, andwith suitable molds in the holders 12, the composite centrifugal castingmachine undergoes repeated cycles of coordinated motion responsive tothe mechanico-hydraulic motivator.

Fresh shell molds are cast, assembled and then continually fed by thebelt conveyor 136 to the loading station 14, where they are loaded oneat a time on the table 10 by the loading arm 90. During one portion ofthe machine cycle, this arm first grips the mold with the jaws 126 undercontrol of motivator section g, then raises bodily under control ofmotivator section e, and then swings horizontally under control ofmotivator section 0. After the mold is thus presented above a newlypresented empty holder 12, the arm lowers and the jaws thereafter opento deposit the mold on the table. The arm will next swing back to thesupply station to get another mold.

Simultaneously, the unloading arm 92 goes through its above-noted cycleunder control of motivator sections b, d and f to grip a filled mold,raise it out of the holder 12, swing it above the shaker screen conveyor140, and release it.

Also, while the table 10 is stopped, the locating and locking finger 78under control of motivator section a holds the table in its newlyindexed position while the rack 54 for the index drive pinion 46 isbeing reset.

Furthermore, during this time, the fluid motor 150, controlled bymotivator section it nudges the secondary fiber drive wheel 144 againsta flywheel 244 presented at station 16 to impart spin to an empty mold;and, the fluid mot-or 224 controlled by motivator section j urges thebrake 220 against a flywheel 244 presented at station 22 to remove spinfrom a partially filled mold.

Finally, during table stop time, the three valves 164, 164' and 164" atstations 18, 20 and 24 are ope-rated by motivator sections i, m and q,respectively, to meter predetermined amounts of different molten metalsto molds positioned at the respective pouring stations.

To meter metal, the valve rod 164 in the casting furnace is raisedslightly from its dished seat 204 by the fluid motor 176 controlled frommotivator section i of the m-echanico-hydraulic motivator. While thevalve rod 164 is oil its seat, metal pressurized by the static head ofmolten metal in the pot 156 flows across the seat 204 and out the outletopening 214 of the valve mechanism and then flows by gravity directlyinto the mold 344. With a given viscosity to the molten metal, a givensize to the orifice 214, and a static head of metal within allowabletolerances, the quantity of metal metered from the casting furnace tothe mold may be very accurately controlled by the amount of time thevalve 164 is held off its seat by the mechanico hydraulic motivator. Thevalve may be closed by operation of the timer controlled solenoid valve328 for disabling the liquid column 326i which actuates the fluid motor176.

During the other portion of the machine cycle, the table 10 may beindexed to shift each mold one step farther along the path beneath thetrio of pouring stations. The drive pinion 46 is raised by the fluidmotor cylinder 72 under control of motivator section I to engage withthe teeth 38 of the table; thereafter, the pinion 46 is rotated by themotor cylinder 58 responsive to motivator section n.

During this latter portion of the machine cycle, of course, the loadingand unloading arms are not working over the table, and the fiber drivewheel 144 and the brake 220 are idled, as are the three metal meteringvalves Eat the pouring stations. Continued rotation of the camshaft 250thus powers and controls repeated cycles of coordinated motion of thevarious parts of the composite centrifugal casting machine of thisinvention.

The casting method of this invention carried out by the above describedmachine is best understood by following the travel of a given mold 344after it is loaded 'on the table at station 14 and until it is unloadedtherefrom at tation 26. First, at station 16, the mold is spun about itsvertical axis.

Then, regarding FIGURE 11, a small predetermined quantity of moltenmetal 356 is metered to the mold at station v18. It falls by gravity tothe bottom and is thence displaced by centrifugal force to theperipheral zone of the mold defining the conical seat of the enginevalve. This forms a ring of molten metal.

As the metal ring cools, its centrifugally inner, or exposed surfacefirst forms a frozen skin which gradually thickens toward the center ofthe quantity. This forms a flow barrier which, when molten metal issubsequently poured onto it, prevents flow of the second molten metalinto the first molten metal on the other side of the barrier.

Regarding FIGURE 12, another small predetermined quantity of a differentmolten metal 358 is also metered to the mold at staiton 20. By [thistime the first quantity of metal 356 is not yet frozen solid, and thesecond quantity 358 flows by gravity and centrifugal force against thebarrier and remains in contact therewith; it fills the mold part way upthe zone defining the concentric operating stem of the engine valve.

Where the two metals meet, the barrier is remelted and the two metalsblend and intermingle in the space occupied by the barrier. If thefirst-poured metal, for instance, has a comparatively high meltingpoint, the second metal will be cast at a temperature high enough toremelt the skin on the first metal before the temperature of the secondmetal falls below such a point. Depending upon the temperatures, meltingpoints, alloy compositions, specific gravities, the amount ofcentrifugal force and the like, the zone of fusion 360 may be fullycontrolled. It Will be an annular zone of'a radial thickness deep enoughfor a thorough bond between the two metals yet limited so that none ofthe second poured metal 358 reaches the outer edge of the casting in thearea that will be the seat of the finished cast valve.

As the blended joint cools, the upper surface of the second poured metal302 also forms a second surface skin or barrier thereon. Burning of themold sand bonding medium continually generates an atmosphere in the moldwhich inhibits oxide formations on the first two shots of metal as theycool. While the inner body of the second metal behind the barrier isstill above the freezing point, however, a third amount of molten metal362 is metered to the mold at station 24, see FIGURE 13, after the axialspin has been subtracted from the mold by the brake 220 at station 22.

This third :amount of metal fills the mold up to the feed cup 354. Itremelts the barrier on the upper surface of the second amount 358 andblends therewith through a juncture zone 364. This latter zone,depending upon the temperatures, melting points, alloy compositions, andthe like may be controlled to provide a strong union with its depthlimited, however, to a predetermined range.

Cooling of the entire casting results in a tri-rnetal valve, after themold and the upper feed sprue are removed, having different metals inthe portions which encounter different conditions in the valvesoperational environment. Regarding FIGURE 14, the flared head portion366 of the cast valve 368 is composed entirely of the second pouredmetal 358. The surrounding conical seat portion 370 is composed entirelyof the first poured metal 356.

Thezone 360 where these two metals blend together is superior to a weldjoint, aside from the obvious cost savings, in that among other thingsthe characteristics of one metal merge or graduate into thecharacteristics of the other over a significant radial extent. There isno abrupt line of demarcation therebetween as in a Weld joint tointerrupt thermal conduction or heat flow from the valve head to theseat, and diverse coefficients of thermal ex- 12 plansion do notoccur'in immediate side by side relations 1p.

The concentric operating stem portion 372 is composed entirely of thethird poured amount of metal 362. The bond or junction at 364 joiningthe stem portion metal with the head portion metal again'has the abovenoted advantages over a common weld joint. 1

Depending upon the metals chosen for the various parts of the valve,heat treatment may be desirable to develop the metallurgical qualitiesdesired. This may involve no more than induction hardening the tip 374of the valve stem 372. Typical examples of metals which may be employedto advantage in exhaust valves for internal combustion engines are asfollows.

The first-poured metal 356 to form the conical seat portion of the valvemay be a cobalt-nickel base metallic alloy. As used herein, acobalt-nickel base alloy is one in which the sum of the cobalt and thenickel percentages by weight is above fifty percent; for instance, thetwo may total above fifty percent, or one or the other alone may exceedfifty percent to be balanced by smaller amounts of the other, or even tothe total exclusion of the other. Such an alloy has excellent resistanceto corrosion from the combustion products of leaded fuels, especially athigh temperatures. Furthermore, it is highly resistantto scuffing andwear. Examples of such having these characteristics are:

1 Maximum.

For the second-poured metal 358 to form the flanged head portion of thevalve, an austenitic steel is preferred. Such a ferrous base alloy hassufficient alloying elements such as manganese, chromium and nickel toform an austenitic structure. Such a steel is not prohibitivelyexpensive and has resistance to corrosion in the manner of the stainlesssteels. Furthermore, it has mechanical properties such as strength andtoughness even in the higher temperature ranges encountered in modernheavy duty internal combustion engines. And, like the cobalt-nickel basealloy, it will not be adversely affected by any heat treatment to whichthe valve stem may subsequently be subjected. Examples of such havingthese characteristics are:

C 1.00 .20 1.00 .25 .50 Mn 7.00 1. 25 1 75 Cr 21. 0O 21. 00 15. 50 26.00 15. 00 Ni... 2. 25 12. 00 14. 00 5. 00 15. 00 S il 1. 00 l 1. 50

1 Maximum. 2 Balance.

Finally, for the third-poured metal 362 to form the operating sternportion of the valve, a steel having sufiicient carbon plus carbidestabilizers so that it will form martensite and can be even furtherhardened by heat treatment is preferred. In this class fall the toolsteels which, even before appropriate hardening, are extremely resistantto mechanical wear from rubbing and sending. While not as corrosionresistant as the cobalt-nickel base alloys nor as tough at hightemperatures as the austenitic steel alloys, it has wear qualities toWithstand the continual rubbing by the cam, rocker arm or other valveactuator. With such steels, after an annular groove is machined on 13the stem of the cast valve, for a spring retainer, further hardening ofthe stem tip may be attained by induction hardening or other knownheating and quenching steps. Examples of such hardenable steel alloyshaving these characteristics are:

1 Minimum. 2 Balance.

These metals are given as examples only, and it will be clear that manyothers in each class may be employed within the scope of the definedinvention depending upon the desired finished product.

FIGURE illustrates a finished valve 368 in its operational environment.A spring retainer 376 is aflixed to the annularly grooved valve stem. Aheavy valve seating spring 378 acts between the retainer and theinternal combustion engine 380 to bias the valve head 366 upwardly sothat the conical seat 370 closes against a mating insert 382 fixed inthe engine. The valve stem 372 is reciprocable in a tubular valve guide384 also fixed in the engine. Downward motion of a valve actuator 386,such as a cam or rocker arm, compresses the valve spring 378 and movesthe valve head downwardly away from the seat insert 382 into thecombustion chamber to open the valve, as is well known, and subsequentupward motion of the actuator 386 allows the spring 378 to again seatthe valve.

Thus a casting machine and method for producing an improved engine valvehave been disclosed. The machine may be used for any number of divergentproducts requiring a first metal on an outside wall and a second metalon the inside, for it will be obvious that one or more of the pouringstations may be rendered inoperative for casting articles of less thanthree metals; on the other hand, more pouring stations may be providedwith mold spinning and braking stations placed as desired forcentrifugally casting articles of more than three metals, all within thescope of the invention.

The method of casting, while entirely suitable for producing internalcombustion engine exhaust valves, also lends itself to casting divergentproducts. Engine valves may be continually cast at the rate of one percycle of the machine-every several seconds. The method is veryinexpensive when considered against the improved product result, and itis made possible by the controlled metering of small predeterminedamounts of high melting temperature metal from a bottom pour furnace.Furthermore, the mechanico-hydraulic motivator aids in controlling thecritical time lapse between successive pours of different molten metalsto a given mold.

Finally, the improved metallurgical characteristics of the disclosedvalve product or article meet a current need in the internal combustionengine industry.

While the above described embodiment constitutes a preferred mode ofcarrying out this invention, many other forms might be adopted withinthe scope of the actual invention, which is variously claimed as:

I claim:

1. A method of casting a small composite article comprising providing amold having a cavity defining the shape of the article, maintainingplural sources of different molten metals at elevated temperatures,placing the mold at one of the sources of molten metal, metering apredetermined amount of one molten metal therefrom to flow by gravityinto the mold cavity, applying a secondary force to overcomegravitational force and displace the molten metal to a desired zone inthe mold cavity, cooling the displaced amount of molten metal to freezeonly a surface skin thereon while placing the mold at another of thesources of molten metal, metering a predetermined amount of anothermolten metal therefrom to flow into the mold cavity into contact withthe displaced amount of molten metal, remelting surface skin on thedisplaced amount of metal where it contacts the newly metered amount ofmetal, gradually cooling both amounts of metal together in the moldcavity and removing the secondary force to provide an autogenouslyunited article having metallurgical characteristics of the one metal inone portion and metallurgical characteristics of the other metal inanother portion.

2. A method of casting a valve of the type having a flanged head portionincluding a peripheral conical seat portion and a generally concentricoperating stem portion comprising placing a ring-shaped quantity ofcobalt-nickel base metallic alloy to form the peripheral seat portioninto contact with a flange-shaped quantity of austenitic steel alloy toform the remainder of the head portion, one of the quantities of alloybeing entirely molten and the other being solid only on its outersurface and otherwise molten when placed in contact, melting the solidouter surface where the two quantities are in contact so that the twoquantities Will blend in the molten state throughout an annular fusionzone of substantial radial extent, and then freezing both quantities ofalloy to form an autogenously united casting having a cobalt-nickel basemetallic alloy seat portion around a head portion of austenitic steelalloy.

3. A method of casting a valve of the type having a flanged head portionincluding a peripheral conical seat portion and a generally concentricoperating stem portion comprising placing a flange-shaped quantity ofaustenitic steel alloy to form the head portion into contact With arod-shaped quantity of hardenable steel alloy to form the stem portion,one of the quantities of steel alloy being entirely molten and the otherbeing solid only on its outer surface and otherwise molten when placedin contact, melting the solid surface where the two quantities are incontact so that the two quantities will blend in the molten statethroughout a limited fusion zone, and then freezing both quantities ofsteel alloy to form an autogenously united casting having an austeniticsteel alloy head portion joined to a stern portion of hardenable steelalloy.

4. A method of casting a valve of the type having a flanged head portionincluding a peripheral conical seat portion and a generally concentricoperating stem portion comprising placing a ring-shaped quantity ofcobalt-nickel base metallic alloy to form the peripheral seat portioninto contact with a flange-shaped quantity of austenitic steel alloy toform the remainder of the head portion, the quantity of austenitic steelalloy being entirely molten and the ring-shaped quantity ofcobalt-nickel base alloy being solid only on its outer surface andotherwise molten when placed in contact, blending the two quantities inthe molten state throughout a limited fusion zone where they contact,freezing the joined quantities of alloy until the flange-shaped quantityis solid in the portion remote from the cobalt-nickel base alloy on onlyits outer surface, then placing a rod-shaped quantity of hardenablesteel alloy to form the stem portion into contact with the solid outersurface of the flange-shaped quantity, the rod-shaped quantity beingentirely molten, and finally blending the austenitic steel alloy withthe hardenable steel alloy throughout a limited fusion zone where theycontact to form thereby an autogenously united casting of a valve havinga cobaltnickel base metallic alloy seat portion around a head portion ofaustenitic steel alloy joined to a stern portion of hardenable steelalloy.

5. A method of casting a valve of the type having a flanged head portionincluding a peripheral conical seat portion and a generally coaxialoperating stem portion comprising providing a shell mold having a cavitydefining the shape of the valve, positioning the mold with the 15 cavityaxis generally vertical, allowing to fiow by gravity into the moldcavity a predetermined quantity of molten cobalt-nickel base metallicalloy, rotating the mold about its cavity axis to displace the moltenalloy radially outwardly by centrifugal force to the zone of the cavitydefining the seat portion of the valve, forming a non-liquid barrier onthe exposed surface of the molten cobalt-nickel alloy then allowing toflow by gravity into the mold cavity a quantity of molten austeniticsteel alloy to fill at least the zone of the cavity defining the headportion of the valve, the latter alloy being hotter than the meltingpoint of the former alloy whereby the barrier will be melted and the twoalloys will blend throughout a substantial juncture zone to provide anautogenously united casting having a cobalt-nickel base metallic alloyseat portion around a head portion of austenitic steel alloy.

6. A method of casting a valve of the type having a flanged head portionincluding a peripheral conical seat portion and a generally coaxialoperating stem portion comprising providing a shell mold having a cavitydefining the shape of the valve, positioning the mold with the cavityaxis generally vertical, allowing to flow by gravity into the moldcavity a predetermined quantity of molten cobalt-nickel base metallicalloy, rotating the mold about its cavity axis to displace the moltenalloy radially outwardly by centrifugal force to fill only the zone ofthe cavity defining the seat portion of the valve, continuing to rotatethe mold at least until a surface skin has begun to freeze on thedisplaced alloy, then allowing to flow by gravity into the mold cavity aquantity of molten austenitic steel alloy to fill the zone of the cavitydefining the head portion of the valve, joining these two alloys wherethey contact each other by remelting surface skin of the cobalt-nickelbase alloy, freezing surface skin on the austenitic steel alloy in thezone of the mold cavity where the valve head portion merges with thestem portion, filling the mold cavity with molten hardenable steelalloy, joining the two steel alloys where they contact each other byremelting surface skin of the austenitic steel alloy, and freezing allthe alloy in the shell mold to provide an autogenously united casting ofa valve having a cobaltnickel base metallic alloy seat portion around ahead portion of austenitic steel alloy joined to a stem portion ofhardenable steel alloy.

7. A method of casting a valve of the type having a flanged head portionincluding a peripheral conical seat portion and a generally coaxialoperating stem portion comprising providing a shell mold having a cavitydefining the shape of the valve, positioning the mold with the cavityaxis generally vertical, allowing to flow by gravity into the moldcavity a predetermined quantity of molten cobalt-nickel base metallicalloy, rotating the mold about its cavity axis to displace the moltenalloy radially outwardly by centrifugal force to fill only the zone ofthe cavity defining the seat portion of the valve, continuing to rotatethe mold at least until a surface skin has begun to freeze on thedisplaced alloy, then allowing to fiow by gravity into the mold cavity aquantity of molten austenitic steel alloy to fill the zone of the cavitydefining the head portion of the valve, joining these two alloys wherethey contact each other by remelting surface skin of the cobalt-nickelbase alloy, freezing surface skin on the austenitic steel alloy in thezone of the mold cavity where the valve head portion merges with thestem portion, filling the mold cavity with molten hardenable steelalloy, joining the two steel alloys where they contact each other byremelting surface skin of the austenitic steel alloy, freezing all thealloy in the shell mold, removing the frozen alloy from the mold andthen heat treating a portion of the hardenable steel alloy to provide anautogenously united casting of a valve having a cobalt-nickel basemetallic alloy seat portion around a head portion of austenitic steelalloy joined to a stem portion of another steel alloy a portin of whichis significantly harder than in the as-cast state.

8. A method of continuously casting valves of the type having a flangedhead portion including a peripheral conical seat portion and a generallycoaxial operating'stem portion comprising shifting in one directionalong a path molds each having a cavity defining the shape of the valve,maintaining a supply of molten cobalt-nickel base metallic alloy at afirst point along the path and a supply of molten austenitic steel alloyat a second point farther along the path, simultaneously metering atpreset time intervals a predetermined quantity of molten alloy from eachsupply into two molds positioned respectively at the first and secondpoints along the path, and axially spinning each mold as it shifts alongthe path to displace the predetermined quantity of molten cobalt-nickelbase alloy therein by centrifugal force to the zone of the mold cavitydefining the peripheral conical seat portion prior to the metering ofthe predetermined quantity of austenitic steel alloy thereinto at thesecond point farther along the path.

9. A method of continuously casting valves of the type having a flangedhead portion including a peripheral conical seat portion and a generallycoaxial operating stem portion comprising shifting in one directionalong a path molds each having a vertically disposed cavity defining theshape of the valve with the stem portion upwards, maintaining a supplyof molten cobalt-nickel base metallic alloy at a first point along thepath and a supply of molten austenitic steel alloy at a second pointfarther along the path and a supply of molten hardenable steel alloy ata third point even farther along the path, simultaneously metering atpreset time intervals at predetermined quantity of molten alloy fromeach supply into three molds positioned respectively at the first,second and third points along the pat-h, adding axial spin to each moldas it shifts along the path to displace the predetermined quantity ofmolten cobalt-nickel base alloy therein by centrifugal force to the zoneof the mold cavity defining the peripheral conical seat portion prior tothe metering of the predetermined quantity of austenitic steel alloythereinto at the second point along the path, and subtracting axial spinfrom each mold prior to the metering of the predetermined quantity ofharden'able steel alloy thereinto at the third point along the path.

10. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange on a rod-shaped stem,which method includes pouring into a valve mold a quantity of moltencobaltnickel base alloy sufficient to form the seat portion, rotatingthe mold to displace the cobalt-nickel alloy against the force ofgravity into the rim of the mold to form the seat portion, forming fromthe cobalt-nickel alloy on the exposed surface thereof a flow barriersufficient to prevent the flow of molten metal through the barrier whilemaintaining the alloy molten adjacent the barrier, pouring onto thebarrier a quantity of austenitic steel alloy sufiicient to occupy only apart of the remainder of the mold and to form at least the remainder ofthe head of the valve, maintaining for a time the austenitic steel andthe cobalt-nickel allow both molten in contact with the barrierthroughout the surface of the barrier, melting the barrier and mixingthe molten cobalt-nickel and the molten austenitic steel alloys in thespace which had been occupied by the barrier, forming from theaustenitic steel on the exposed surface thereof a second flow barriersufiicient to prevent flow of molten metal through the barrier whilemaintaining the austenitic steel molten adjacent the second barrier,pouring onto the second barrier a quantity of molten harden-able steelalloy sufficient to fill the remainder of the mold and form at leastpart of the stem of the valve, keeping molten for a time both theaustenitic steel and the hardenable steel adjacent the second barrier,melting the second barrier and mixing the molten austenitic steel andmolten har-cl'enable steel in the space occupied by the barrier, andcooling all three metals to form a valve having a cobalt-nickel alloyseat portion autogenously united to an austenitic steel head 17 in ajuncture zone of substantial radial extent formed in the space which hadbeen occupied by the first barrier by a progressive blend of metalranging from cobaltnickel alloy to austenitic steel alloy and having ahardenable steel stem autogenously united'to the head in a juncture zoneof substantial axial extent formed in the space which had been occupiedby the second barrier by a progressive blend of metal ranging fromaustenitic steel alloy to hardenable steel alloy.

11. The method of casting "a generally T-shaped engine valve having aperipheral conical seat portion on a head flange on a rod-shaped stem,which method includes pouring into a valve mold a quantity of moltenfirst metal suflicient to form the seat portion, rotating the mold todisplace the molten metal against the force of gravity into the rim ofthe mold to form the seat portion, forming from the first metal on theexposed surface thereof a flow barrier sufficient to prevent the flow ofmolten metal through the barrier while maintaining the metal moltenadjacent the barrier, pouring onto the barrier a quantity of a secondmetal sufiicient to occupy only a part of the remainder of the mold andto form at least the remainder of the head of the valve, maintaining fora time the second metal and the first metal both molten in contact withthe barrier throughout the surface of the barrier, melting the barrierand mixing the molten metals in the space which had been occupied by thebarrier, forming from the second metal on the exposed surface thereof asecond flow barrier sufiicient to prevent flow of molten metal throughthe barrier while maintaining the second metal molten adjacent thesecond barrier, pouring onto the second barrier a quantity of moltenthird metal sufficient to fill the remainder of the mold and form atleast part of the stem of the valve, keeping molten for a time both thesecond metal and the third metal adjacent the second barrier, meltingthe second barrier and mixing the molten second and third metals in thespace occupied by the barrier, and cooling all three metals to form avalve having a seat portion of one metal autogenously united to a headof another metal in a juncture zone of substantial radial extent formedin the space which had been occupied by the first barrier by aprogressive blend of metal ranging from the first metal to the secondand having a stem of a third metal autogenously united to the head in ajuncture zone of substantial axial extent formed in the space which hadbeen occupied by the second barrier by a progressive blend of metalranging from the second metal to the third metal.

12. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange, which method includespouring into a valve mold a quantity of molten cobalt-nickel base alloysufficient to form the seat portion, rotating the mold to displace thecobalt-nickel alloy against the force of gravity into the rim of themold to form the seat portion, forming from the cobalt-nickel alloy onthe exposed surface thereof a flow barrier suflicient to prevent theflow of molten metal through the barrier while maintaining the alloymolten adjacent the barrier, pouring onto the barrier a quantity ofaustenitic steel alloy suflicient to form at least the remainder of thehead of the valve, maintaining for a time the austenitic steel and thecobalt-nickel alloy both molten in contact with the barrier throughoutthe surface of the barrier, melting the barrier and mixing the moltencobalt-nickel and the molten austenitic steel alloys in the space whichhad been occupied by the barrier, and cooling both metals to form avalve having a cobaltnickel alloy seat portion autogenously united to anaustenitic steel head in a juncture zone of substantial radial extentformed in the space which had been occupied by the barrier by aprogressive blend of metal ranging from cobalt-nickel alloy toaustenitic steel alloy.

13. The method of casting a generally T-shaped engine valve having ahead flange on a rod-shaped stem, which method includes pouring into avalve mold a quantity of austenitic steel alloy sufficient to occupyonly a part of the mold and to form at least a part of the head of thevalve, forming from the austenitic steel on the exposed surface thereofa flow barrier suflicient to prevent flow of molten metal through thebarrier while maintaining the austenitic steel molten adjacent thebarrier, pouring onto the barrier a quantity of molten hardenable steelalloy sufiicient to form at least part of the stern of the valve,keeping molten for a time both the austenitic steel and the hardenablesteel adjacent the barrier, melting the barrier and mixing the moltenaustenitic steel and molten hardenable steel in the space occupied bythe barrier, and cooling both metals to form a valve having a hardenablesteel stem autogenously united to an austenitic steel head in a juncturezone of substantial axial extent formed in the space which had beenoccupied by the barrier by a progressive blend of metal ranging fromaustenitic steel alloy to hardenable steel alloy.

14. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange, which method includespouring into a valve mold a quantity of molten first metal sufficient toform the seat portion, rotating the mold to displace the molten metalagainst the force of gravity into the rim of the mold to form the seatportion, forming from the first metal on the exposed surface thereof aflow barrier suflicient to prevent the flow of molten metal through thebarrier while maintaining the metal molten adjacent the barrier, pouringonto the barrier a quantity of a second metal sutficient to form atleast the remainder of the head of the valve, maintaining for a time thesecond metal and the first metal both molten in contact with the barrierthroughout the surface of the barrier, melting the barrier and mixingthe molten metals in the space which had been occupied by the barrier,and cooling both metals to form a valve having a seat portion of onemetal autogenously united to a head of another metal in a juncture zoneof substantial radial extent formed in the space which had been occupied'by the barrier by a progressive blend of metal ranging from the firstmetal to the second.

15. The method of casting a generally T-shaped engine valve having ahead flange on a rod-shaped stem, which method includes pouring into avalve mold a quantity of molten first metal sufiicient to occupy only apart of the mold and to form at least a part of the head of the valve,forming from the first metal on the exposed surface thereof a flowbarrier sufficient to prevent flow of molten metal through the barrierwhile maintaining the metal molten adjacent the barrier, pouring ontothe barrier a quantity of molten second metal sufficient to form atleast part of the stem of the valve, keeping both metals molten for atime adjacent the barrier, melting the barrier and mixing the moltenmetals in the space occupied by the barrier, and cooling both metals toform a valve having a stem of one metal autogenously united to a head ofanother metal in a juncture zone of substantial axial extent formed inthe space which had been occupied by the barrier by a progressive blendof metal ranging from one metal to the other.

16. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange on a rod-shaped stern,which method includes pouring into a valve mold a quantity of moltencobalt-nickel base alloy sufiicient to form the seat portion, rotatingthe mold to displace the cobalt-nickel alloy against the force ofgravity into the rim of the mold to form the seat portion, pouring ontothe cobalt-nickel alloy a quantity of austenitic steel alloy sufiicientto occupy only a part of the remainder of the mold and to form at leastthe remainder of the head of the valve. mixing the molten cobalt-nickeland the molten austenitic steel alloys while controlling the radialextent of mixing at the interface, pouring 'onto the austenitic steel aquantity of molten hardenable steel alloy suflicient to fill theremainder of the mold and form at least part of the stem of the valve,mixing the molten austenitic steel and molten hardenable steel whilecontrolling the axial extent of mixing at the interface, and cooling allthree metals to form a valve having a cobalt-nickel alloy seat portionautogenously united to an austenitic steel head in a juncture zone ofsubstantialbut limited radial extent formed -by a progressive blend ofmetal ranging from cobalt-nickel alloy to austenitic steel alloy andhaving a hardenable steel stern autogenously united to the head in ajuncture zone of substantial but limited extent by a progressive blendof metal ranging from austenitic steel alloy to hardenable steel alloy.

17. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange on a rod-shaped stem,which method includes pouring into a valve mold a quantity of moltenfirst metal sufficient to form the seat portion, rotating the mold todisplace the molten metal against the force of gravity into the rim ofthe mold to form the seat portion, pouring onto the first metal aquantity of a second metal sufficient to occupy only a part of theremainder of the mold and to form at least the remainder of the head ofthe valve, mixing the molten metals while controlling the radial extentof mixing at the interface, pouring onto the second metal a quantity ofmolten third metal suflicient to fill the remainder of the mold and format least part of the stem of the valve, mixing the molten second andthird metals while controlling the axial extent of mixing at theinterface, and cooling all three metals to form a valve having a seatportion of one metal autogenously united to a head of another metal in ajuncture zone of substantial but limited radial extent by a progressiveblend of metal ranging from the first metal to the second and having astern of a third metal autogenously united to the head in a juncturezone of substantial but limited axial extent by a progressive blend ofmetal ranging from the second metal to the third metal.

18. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange, which method includespouring into a valve mold a quantity of molten cobalt-nickel base alloysutficient to form the seat portion, rotating the mold to displace thecobalt-nickel alloy against the force of gravity into the rim of themold to form the seat portion, pouring onto the cobalt-nickel alloy aquantity of austenitic steel alloy sufiicient to form at least theremainder of the head of the valve, mixing the molten cobalt-nickel andthe molten austenitic steel alloys while controlling the radial extentof mixing at the interface, and cooling both metals to form a valvehaving a cobalt-nickel alloy seat portion autogenous- 1y united to anaustenitic steel head in a juncture zone of substantial but limitedradial extent formed by a progressive blend of metal ranging fromcobalt-nickel alloy to austenitic steel alloy.

19. The method of casting a generally T-shaped engine valve having aperipheral conical seat portion on a head flange, which method includespouring into a valve mold a quantity of molten first metal suflicient toform the seat czi portion, rotating the mold to displace the moltenmetal against the force of gravity into the rim of the mold to form theseat portion, pouring onto the first metal a quantity of a second metalsufficient to form at least the remainder of the head of thevalve,rnixing the molten metals while controlling the radial extent ofmixing at the interface, and cooling both metals'to form a valve havinga seat portion of one metal autogenously united to a head of anothermetal in a juncture zone of substantial but limited radial extent formedby a progressive blend of metal ranging from the first metal to thesecond.

20, The method of casting a generally T-shaped engine valve having ahead flange on a rod-shaped-stem, which method includes pouring into avalve mold a quantity of molten austenitic steel alloy suflicient tooccupy'only apart of the mold and to form at least part of the head ofthe valve, pouring onto the austenitic steela quantity of moltenhardenable steel alloy sufiicient to fill the remainder of the mold andform at least part of the stem of the valve, mixing the moltenaustenitic steel and molten hardenable steel While controlling the axialextent of mixing, and coo-ling both metals to form a valve having ahardenable steel stern autogenously united to an austenitic steel headina juncture zone of substantial but limited axial extent by a progressiveblend of metal ranging from austenitic steel alloy to hardenable steelalloy.

21. The method of casting a generally T-shaped engine valve having ahead flange on a rod-shaped stem, which method includes pouring into avalve mold a quantity .of molten first metal sufficient to form at leastpart of the head of the valve, pouring onto the first metal a quantityof molten second metal sufiicient to fill the remainder of the mold andform at least part of the stern of the valve, mixing the molten metalswhile controlling the axial extent of mixing at the interface, andcooling the metals to form a valve having a stem of one metalautogenously united to the head in a juncture zone of substantial butlimited axial extent formed by a progressive blend of metal ranging fromone metal to the other metal.

References Cited UNITED STATES PATENTS 2,483,849 10/1949 Seaman 222062,837,799 6/1958 Priebe et al. 22206 2,294,803 9/1942 Rich -2 1231882,881,750 4/1959 Hanink 123188 1,885,465 11/ 1932 Moulton 225851,917,872 7/1933 Campbell 2258.5 1,423,876 7/1922 Pfanstiehl 123-1881,444,210 2/1923 Rich 123-188 1,770,582 7/1930 Greiner et a1 22200.51,806,972 5/1931 McCarroll et al.

2,270,822 1/ 1942 Cape.

2,479,039 8/1949 Cronstedt 22205 2,495,731 1/1950 Jennings l23-1881,770,582 7/1930 Pike 222005 2,710,997 6/1955 Krepps 22200.5

J. SPENCER OVERHOLSER, Primary Examiner.

1. A METHOD OF CASTING A SMALL COMPOSITE ARTICLE COMPRISING PROVIDING AMOLD HAVING A CAVITY DEFINING THE SHAPE OF THE ARTICLE, MAINTAININGPLURAL SOURCES OF DIFFERENT MOLTEN METALS AT ELEVATED TEMPERATURES,PLACING THE MOLD AT ONE OF THE SOURCES OF MOLTEN METAL, METERING APREDETERMINED AMOUNT OF ONE MOLTEN METAL THEREFROM TO FLOW BY GRAVITYINTO THE MOLD CAVITY, APLYING A SECONDARY FORCE TO OVERCOMEGRAVITATIONAL FORCE AND DISPLACE THE MOLTEN METAL TO A DESIRED ZONE INTHE MOLD CAVITY, COOLING THE DISPLACED AMOUNT OF MOLTEN METAL TO FREEZEONLY A SURFACE SKIN THEREON WHILE PLACING THE MOLD AT ANOTHER OF THESOURCES OF MOLTEN METAL, METERING A PREDETERMINED AMOUNT OF ANOTHERMOLTEN METAL THEREFROM TO FLOW INTO THE MOLD CAVITY INTO CONTACT WITHTHE DISPLACED AMOUNT OF MOLTEN METAL, REMELTING SURFACE SKIN ON THEDISPLACED AMOUNT OF METAL WHERE IT CONTACTS THE NEWLY METERED AMOUNT OFMETAL, GRADUALLY COOLING BOTH AMOUNTS OF METAL TOGETHER IN THE MOLDCAVITY AND REMOVING THE SECONDARY FORCE TO PROVIDE AN AUTOGENEOUSLYUNITED ARTICLE HAVING METALLURGICAL CHARACTERISTICS OF THE ONE METAL INONE PORTION AND METALLURGICAL CHARACTERISTICS OF THE OTHER METAL INANOTHER PORTION.